What is the intended use for this combination and how high do you want to turn it?
The 12.5 pistons you have and E-85 would work but you'd need to run a Holley or a Holley knock off.
The ones I’m considering (Egge) are supposedly 10:1. There were forged TRW 12.5:1 pistons made back in the day - allegedly.
The intended use is weekend drag race and the occasional parking lot donut.
